The broad goals of the project are to increase our understanding of the role of numerical processes and quantity judgments in guiding behavior, especially under conditions of conflicting behavioral dispositions arising from discordant incentive features and reward consequences of the choice options. Of special interest is the utility of numerical symbols in particular, and symbolic representations more generally, in maximizing sensitivity to the consequences of behavioral actions by minimizing conflicts from direct incentive biases that can lead to non-optimal choice. These issues will be addressed in comparative studies, with chimpanzees and monkeys, of a powerful task interference effect. Despite their demonstrated competence in a variety of sophisticated cognitive tasks, chimpanzees are unable to select the smaller of two arrays of food items, in order to receive the large reward. This interference effect appears to arise from a direct incentive bias toward the larger array, reminiscent of the impulsive behavior of children as documented in the self-control literature., When Arabic numerals (which the animals have been trained to use as number labels) are substituted for the food arrays, the animals perform more optimally in the choice task. The proposed studies will explore the nature of quantity judgments with object arrays and numeric symbols, and the determinants and underlying mechanisms of the task- interference effect. These studies should into the evolutionary origins of numerical capacities, their function in behavior, and the special role of symbolic representations in guiding behavior. Given the unique phylogenetic status of chimpanzees, this species may be optimal for bridging the gap between the human and animal literatures on numerical processes. In view of the ubiquity and importance of quantity-based information and quantity judgments in human and animal behavior, illumination of the relationships between numerical processes and behavioral action would have broad significance for basic behavioral research and mental health. Resulting theory and data would be relevant to an understanding of emotion, conflict, motivation, and the nature and dynamics of human attitudes and their influences on behavior.